docs: def sub_menu(request, page_id):
      """Render the children of the requested page with the sub_menu
      template."""
      page = Page.objects.get(id=page_id)
      pages = page.children.all()
      page_languages = settings.PAGE_LANGUAGES
      return render(request, "admin/pages/page/sub_menu.html", {
          'can_publish': request.user.has_perm('pages.can_publish'),
          'page': page,
          'pages': pages,
          'page_languages': page_languages,
      })